Variable power drive system



Dec. 10, 1963 R. EDWARDS 3,114,091

VARIABLE POWER DRIVE SYSTEM Filed Feb. 9. 1960 2 Sheets-Sheet l '74 2 ll/2 V VARIABLE g OSCILLATOR AMPLIFIER AMPL'F'ER DRIVER OUTPUT TRANSDUCERFIG. 2.

INVENTOR. ROBERT EDWARDS his ATTORNEYS.

Dec. 10, 1963 R. EDWARDS 3,114,091

VARIABLE POWER DRIVE SYSTEM Filed Feb. 9, 1960 2 Sheets-Sheet 2TRANSISTOR 25 COLLECTOR (CONTROL RESISTOR 22 SET AT LOW VALUE)TRANSISTOR 25 COLLECTOR (b) (CONTROL RESISTOR 22 SET AT HIGH VALUE)SECONDARY WINDING 29 (CONTROL RESISTOR 22. SET AT LOW VALUE) SECONDARYWINDING 29 (CONTROL RESISTOR 22 SET AT HIGH VALUE) IN VEN TOR. ROBERTEDWARDS his ATTORNEYS.

United States Patent 0.

3,114,091 VARIABLE POWER DRIVE SYSTEM Robert Edwards, Westfield, N.J.,assignor to Electronic Assistance Corporation, Red Bank, NJ acorporation of New York Filed Feb. 9, 1966, Ser. No. 7,655 '7 Uaims.(Cl. 318-118) This invention relates to an electrical drive system and,more particularly, to a drive system for a transducer having means tovary the power output.

Many transducer drive systems have been provided in the past fordelivering an ultrasonically varying voltage and a relatively highamount of power. These circuits have proved to have seriousdisadvantages, however, in that they have very low eiliciency ratings,require a cooling system because they generatetoo much heat, anddissipate too much power at the power varying means. Another seriousproblem has been in matching impcdances between the transducer beingdriven and the system.

Accordingly, it is a purpose of this invention to provide a variablepower drive system for a transducer that obviates the above-describeddisadvantages. This purpose is attained, in accordance with a preferredembodiment of the invention, by providing a transistorized system thatincludes first circuit means for generating a varying voltage having atleast first and second portions, the first portion having a positivepolarity relative to the second portion, second circuit means connectedto be responsive to the first circuit means for varying the timeduration of one of the portions of the varying voltage,

and third circuit means connected to be responsive to the second circuitmeans and including a switching element that is controlled by thevoltage output from the second circuit means. The switching element may,for example, control the flow of power from an electrical potentialsource to a transducer or other power consuming element. The secondcircuit includes means for varying the time duration of one of theportions of the voltage so that it is able to vary the power output ofthe system without changing the frequency of recurrence of the varyingvoltage. Since most or all of the above-described circuits can betransistorized, the system has other substantial advantages in that itconsumes very small amounts of power and impedance matching problems aresubstantially eliminated.

This invention may be more completely understood from the followingdetailed description of a representative embodiment of the inventiontaken in conjunction with the accompanying figures of the drawings inwhich:

FIGURE 1 is a block diagram of a variable power drive system constructedin accordance with the invention;

FIGURE 2 is a schematic diagram of the system illustrated in FIGURE 1;and

FIGURE 3 is a schedule of waveforms for a portion of the systemillustrated in FIGURES l and 2.

With reference to FIGURE 1, the variable power drive system includesanoscillator which generates a periodically varying voltage, an amplifierill, a variable amplifier 12 which is provided with a manually variablepower control, a driver stage 13, and an output transformer 14. Theprimary winding of the transformer 14 is connected in the output circuitof the driver 13 and Edi hddl its secondary winding is connected to apower consuming device (not shown). These elements are illustratedschematically in FIGURE 2. V

The oscillator 10 includes a p-n-p transistor 15 that is connected in anemitter-driven Hartley oscillator type circuit. Its tank circuit iscomposed of a center-tapped inductor 16, that is connected in parallelwith a capacitor ii', the values of which are set in accordance with thefrequency desired. The feed-back for the circuit is provided by acapacitor 18 that is connected between the hot terminal of the tankcircuit and the base electrode of the transistor 15. The operating pointof the oscillator circuit is stabilized and the waveform regulated by Ia resistor 19 that is connected in the emitter circuit of the transistor5.

The output of the oscillator circuit 19 is connected to the baseelectrode of a transistor 2%) in the amplifier 11 through a resistor 21.The resulting output waveform on the collector electrode of thetransistor 20 is a short rectangular positive going pulse that has arepetition rate equal to the frequency of the oscillator it The couplingbetween the amplifier 11 and the variable amplifier 12 is through avariable resistor 22 and a parallel capacitor 23, and is such that atransistor 24 in the variable amplifier 1 .2 is normally saturated. Inoperation, the waveform obtained from the collector electrode of thetransistor 2% cuts oil the transistor 2 with the result that thewaveform on the collector electrode of the transistor 24 is also arectangular pulse but has a negative polarity. The time duration of thislatter negative rectangular pulse is variable and is determined by thedegree of saturation into which the transistor 24- is driven, whichinturn is controlled by the setting of the variable resistor 22.

The driver circuit 13 includes a transistor 25 that has its baseelectrode connected to the collector electrode of the transistor 24through a coupling circuit that includes a resistor 26 and a parallelcapacitor 27. A preferred type of transistor for this stage is adiffused base p-n-p transistor which, in operation, is driven fromcutoli into saturation by the output voltage from the variable amplifier12. A DC. potential source is connected across a pair of terminals 33and, when the transistor 25 is saturated, causes current to fiow throughthe primary winding 28 of the transformer 14, the transistor 25 and aresistor 36. Since the transistor 25 is being turned on and 0d, apowerful rectangular pulse appears at the winding 255.

The output stage for this system includes the primary winding 2? and thesecondary winding 29 which are wound on a core 3% of magnetic material.A resistor 31 and a capacitor 32 are connected in parallel with theprimary winding 28 to make a tuned circuit. A tran ducer 3'. isconnected during operation across the secondary winding 29 and the DC.potential source connected to the terminals 33 provides the necessaryoperating potentials for the transistor circuits 1%, l1 and 12.

The variable power drive system described may be connected to drive anultrasonic generator. If large quantities of power are required, a bankof these systems can be coupled in parallel on thecore 34 of thetransformer l4, and the secondary winding 29 can be coupled to a magnetos-trictive element in the ultrasonic generator. The elements inthe oscillator circuit 16 are preferably Patentedfiec. it 19:33

set so that they frequency of oscillation is equal to the resonantfrequency of the magnetostrictive element, and the tuned circuitcomposed of the winding 23, the resistor 31, and the capacitor 32 isalso set at this frequency. During operation the varying voltagegenerated by the oscillator it? alternately drives the transistor 25from. cut-oil to saturation and causes current to flow in the secondarywinding 29 of the transformer 14. This current flows through a windingthat is inductively coupled with the magnetostrictive element in theultrasonic generator and causes this element to expand and contract atthe frequency of the oscillator.

The power output of the transducer is varied by changing the amount oftime that current flows through the secondary winding 29. This is doneby varying the time duration or the width of the portion of the voltagethat drives the transistor 25 into saturation. This is best illustratedby the schedule of Waveforms shown in FIG- URE 3. When the variablecontrol resistor 22. is set at a low resistance value, the Waveformappearing at the collector electrode of the transistor 25 is representedby the waveform (a), FIGURE 3, and the positive going portion has arelatively short width or time duration. When the control resistor 22 isset at o. relatively high value, the positive going portion of thevoltage appearing on the collector of this transistor, represented bythe waveform (b), has a greater width. The voltages appearing at thesecondary winding terminals 23 when the variable resistor 22 is atrelatively low and high values are represented by the waveforms (c) and(01), respectively. An important feature to be noted here is that thenegative going portions of the waveforms (a) and (b) have relativelyconstant peak values irrespective of the setting of the control resistorZ2, and that the frequency remains the same regardless of the setting.These waveforms have a powerful and fast positive rise time which isnecessary to cut on: the driver stage 13 and at the same time ensures afull saturating voltage during the conduction of the driver stage.

If a bank of these systems is being used to drive a single transducer,they can also be connected in parallel by providing each system with aseparate transformer 14 and connecting the outputs in parallel at thetransducer. Regardless of how the systems are connected to thetransducer, all of the oscillators will have to be coupled together insuch a manner that they will oscillate in phase.

While a representative embodiment of the present invention has beenshown and described for purposes of illustration, it is apparent thatthe embodiment is susceptible of change and modification withoutdeparting from this invention in its broader aspects. Therefore, theinvention described herein is not to be construed as limited to thespecific embodiment described but is intended to encompass allmodifications thereof coming within the scope of the follovn'ng claims.

I claim:

1. A variable power drive system comprising oscillator circuit means forgenerating a cyclically varying voltage having at least first and secondportions in each cycle, the first portion having a positive polarityrelative to the second portion, first circuit means connected to beresponsive to the oscillator circuit means for varying the time durationof one of the portions relative to the other of the portions, the firstcircuit means including a transistor element having a base electrodethat is connected to the output of the oscillator means through avariable resistance means, said transistor being normally biased intosaturation and responsive to said cyclically varying voltage toalternately switch between said saturation condition and a lessconductive condition, said variable impedance I sing operative to varythe relative durations of said two conditions within each cycle of saidvarying voltage, and second circuit means connected to be responsive tothe first circuit means and including a switching element that isadapted to be opened by one of the portions of the volt age from thefirst circuit means.

2. A variable power drive system comprising irst circuit means forgenerating a varying voltage having at least first and second portions,the first portion having a positive polarity relative to the secondportion; second circuit rs 'respon sive to the hrs-t circuit means forvary ing the time duration of one of the portions relative to the otherof the portions, the second circuit means including a first transistorhaving base, collector, and emitter electrodes and its base electrodeconnected through a variable resistor means to the output of the firstcircuit means, said first transistor being normally biased intosaturation and responsive to said varying voltage to switch between saidsaturation condition and a less conductive condition, said variableimpedance being operative to vary the relative durations of said twoconditions, and third circuit means including a second transistor havingbase, collector, and emitter electrodes and its base electrode connectedto be responsive to the output voltage from the second circuit means;and the emitter and collector electrodes of the second transistor beingadapted to be connected in series with a power consuming device and asource of electric potential.

3. A generator system comprising first circuit means for generating aregularly varying voltage having at least first and second portions, thefirst portion having a positive polarity relative to the second portion;second circuit means connected to be responsive to the first circuitmeans for varying the time duration of one of the portions of thevarying voltage, the second circuit means including a first transistorhaving base, collector, and emitter electrodes and its base electrodeconnected through a variable resistor and capacitor parallel combinationto be responsive to the output voltage fromthe first circuit means;third circuit means connected to be responsive to the second circuitmeans and including a second transistor having base, collector, andemitter electrodes and its base electrode connected to the output of thesecond circuit means; a Winding and a source of electric potentialconnected in series with the collector and emitter electrodes of thesecond transducer, and a transducer having a magnetostrictive elementinductively coupled with the winding.

4. in a variable power generator system for driving a magnetostrictiveelement, a source of periodic pulses, a transistor having emitter, baseand collector electrodes and norm-ally biased into saturation, variableimpedance means coupling said periodic pulse source to the baseelectrode of said transistor to alternately switch said transistorbetween saturation and cut-cit conditions in synchron-ism with saidpulses, said variable impedance eing operative to vary the duration ofsaid saturation condition with respect to said cut-oil condition of saidtransistor within each cycle of operation thereof, and means to derivean output from said transistor.

5. The invention of claim 4 above wherein said variable impedancecomprises adjustable resistance element.

6. A circuit arrangement for providing controllable amounts of power toa load in regular recurring fashion comprising, a source of regularlyrecurring pulses of relatively low power, a transistor having emitter,base, and collector electrodes and normally biased into saturation,variable impedance means coupling said pulse source to the base electode of said transistor to switch said transistor rallternately betweensaturation and cut-oli in synchronism with said pulses, said variableimpedance means being operative to vary the relative durations of saidsaturation and cu t-oi? conditions within each recurring cycle or"operation thereof, a relatively high power transistor amplifier, meanscoupling the output of said transistor to the input of said amplifier,and means coupling the output of said amplifier to said load.

7. A c cuit arrangement for providing controllable amounts of powe toload in re u lar recurring fashion comprising, a source of cyclicallyvarying voltage, a transistor having emitter, base and collectorelectrodes and norm-ally biased into a saturation condition, variableim- 5 pedance means coupling s aid cyclically varying voltage to thebase eleotrode of said transistot to alternately switch said transistorbetween said saturation condition and a less lCOHdUJO'lIlV6 condition insychronisun with said cyclically vaa'yving voltage, said variableimpedance means being operative to vary the duration of said saturationcondition with mespeot to said less conductive condition of saidtransistor within each cyole of openation thereof, and means to couplethe output of said transistor -00 said load.

References Cited in the file of this patent UNITED STATES PATENTSJaeschke Oct. 13, Dickenson Oct. 8, Henle Nov. 18, Walsh Nov. 18,Clapper Dec. 9, Carlin Sept. 6,

Robinson May 1,

3. A GENERATOR SYSTEM COMPRISING FIRST CIRCUIT MEANS FOR GENERATING AREGULARLY VARYING VOLTAGE HAVING AT LEAST FIRST AND SECOND PORTIONS, THEFIRST PORTION HAVING A POSITIVE POLARITY RELATIVE TO THE SECOND PORTION;SECOND CIRCUIT MEANS CONNECTED TO BE RESPONSIVE TO THE FIRST CIRCUITMEANS FOR VARYING THE TIME DURATION OF ONE OF THE PORTIONS OF THEVARYING VOLTAGE, THE SECOND CIRCUIT MEANS INCLUDING A FIRST TRANSISTORHAVING BASE, COLLECTOR, AND EMITTER ELECTRODES AND ITS BASE ELECTRODECONNECTED THROUGH A VARIABLE RESISTOR AND CAPACITOR PARALLEL COMBINATIONTO BE RESPONSIVE TO THE OUTPUT VOLTAGE FROM THE FIRST CIRCUIT MEANS;THIRD CIRCUIT MEANS CONNECTED TO BE RESPONSIVE TO THE SECOND CIRCUITMEANS AND INCLUDING A SECOND TRANSISTOR HAVING BASE, COLLECTOR, ANDEMITTER ELECTRODES AND ITS BASE ELECTRODE CONNECTED TO THE OUTPUT OF THESECOND CIRCUIT MEANS; A WINDING AND A SOURCE OF ELECTRIC POTENTIALCONNECTED IN SERIES WITH THE COLLECTOR AND EMITTER ELECTRODES OF THESECOND TRANSDUCER, AND A TRANSDUCER HAVING A MAGNETOSTRICTIVE ELEMENTINDUCTIVELY COUPLED WITH THE WINDING.